In recent years, optical communication networks have been widespread and new optical communication networks are being built in various places. For the spread of optical communication networks, there is a demand for cost reduction.
An optical amplifier for amplifying an optical signal transmitted via an optical fiber is an important element of the optical communication network. As an optical amplifier, a rare earth doped optical fiber amplifier is known. As an example of a typical rare earth element doped optical fiber, an optical amplifier (EDFA: EDF Amplifier) using an erbium-doped optical fiber (EDF: Erbium-Doped Fiber) is known. As another example of the optical amplifier, a Raman amplifier for amplifying an optical signal by using stimulated Raman scattering of the optical fiber used as a general transmission line is known.
In conjunction with the above description, an optical fiber amplifier is described in Japanese Patent Application Publication (JP-P2004-282025A). Also, an optical amplifier is described in Japanese Patent Application Publication (JP-P2006-120969A). Also, an optical surge-capable optical receiver is described in Japanese Patent Application Publication (JP-A-Heisei 9-312618). In addition, an optical amplifier is described in Japanese Patent Application Publication (JP-P2002-084024A).